Electric brakes of the type in which a friction pad is pressed against a brake disk by an electric motor to apply a brake are disclosed e.g. in the below-identified Patent documents 1 and 2.
These electric brakes include a linear motion mechanism for converting the rotation of the electric motor to a linear motion. To covert rotation to a linear motion, the linear motion mechanism includes e.g. a ball-screw mechanism (as disclosed in Patent document 1) or a planetary reduction gear mechanism (as disclosed in Patent document 2).
In order to control the braking force, it is necessary to provide such an electric brake with a load detecting sensor.
Such a load detecting sensor is described with reference to a magnetic load sensor 24 used in an electric brake 2 shown in FIG. 1, which embodies the present invention. The magnetic load sensor 24 includes a load detection sensor in the form of a magnetic load sensor 24. As shown in FIGS. 1 and 4, the magnetic load sensor 24 includes a flange member 40 and a support member 41 which are in the form of annular plates axially spaced apart from and axially facing each other, a magnetic target 42 which generates a magnetic field, and a magnetic sensor element 43 capable of detecting a magnetic field. The support member 41 is mounted on a rotary shaft 20 at a position axially rearwardly of the flange member 40. The magnetic sensor element 43 and the magnetic target 42 face each other in a direction perpendicular to the rotary shaft 20.
As a result, when a friction pad 5 is pressed against a brake disk 7 by a linear motion mechanism 6, due to the reaction force that acts on the linear motion mechanism 6, an axial load is applied to the flange member 40 in the direction toward the support member 41 so as to axially deflect the flange member 40 about the outer peripheral portion of the flange member 40. The deflection of the flange member 40 causes a change in the axial relative position between the magnetic target 42 and the magnetic sensor 43. This makes it possible to detect the load on the friction pad 5 based on the output signal of the magnetic sensor 43.
Thus, the electric motor 1 is actuated to control the braking force such that the difference between the above detected value and the target value (amount of depression of the brake pedal) is zero.